This invention relates to sealed and lubricated pivot pins and, more particularly, it concerns such a pivot pin assembly for use in pivoting joints in linkage components of earth-moving equipment.
Typically, loader buckets for earth-moving equipment have vertical plate-like brackets or lugs extending from the back side of the bucket. These brackets are connected to an eye in the end of a loader arm or boom by a transverse pivot pin as shown, for example, in U.S. Pat. Nos. 4,188,146 issued to G. L. Stecklein on Feb. 12, 1980, 4,243,341 issued to S. Kabay et al on Jan. 6, 1981, and 4,400,898 issued to R. B. Christensen on Aug. 30, 1983.
Conventionally, the pivot pin is restrained from rotating relative to the bucket brackets in order to eliminate wear between the pivot pin and the brackets Relative rotation does occur between the eye of the loader arm and the pivot pin. As such, a cylindrical bushing is fixed within the eye of the loader arm and lubrication is provided between the bushing and the pivot pin. In order to keep the bushing lubricated and to keep contaminants and debris from getting between the bushing and the pivot pin, annular seals are provided adjacent each end of the bushing. Examples of such sealed and lubricated pivot pin arrangements are disclosed in U.S. Pat. Nos. 4,096,957 issued to C. P. Iverson et al on June 27, 1978, 4,251,182 issued to W. L. Schroeder on Feb. 17, 1981, and 4,398,862 issued to W. L. Schroeder on Aug. 16, 1983.
Other common pivoting joints in the linkage of earth-moving equipment, such as, loader arm to loader frame and lift cylinder to loader frame, are also adapted to the use of sealed and lubricated pivot pins. All of these pivoting joints and especially the loader arm to bucket joint are subjected to extreme conditions during operation of the equipment. Thus, these joints must be periodically lubricated to flush out contaminants such as grit and moisture and to insure proper lubrication in order to reduce wear and corrosion of the moving parts.
In recent years, more reliable sealing methods have been developed and lubricant reservoirs have been added in order to extend the time interval for required relubrication of the joints. For example, U.S. Pat. No. 4,772,150 issued to L. A. Horton on Sept. 20, 1988 discloses a pin assembly including an improved seal and reservoir arrangement.
One problem associated with a large number of the existing sealed and lubricated pivot pin assemblies is that they require the use of shims during assembly to establish proper clearances between the seals and their mating surfaces. The use of shims to correct for manufacturing tolerances, variations between different makes and models of machinery, and the like not only makes joint assembly time consuming, but also makes the use of the proper number and size of shims and, as such, the skill of the assembler critical to the success of the seals and of the joint itself.
Another problem associated with many of the conventional pivot pin designs is that they are sensitive to axial defections of the bucket brackets or lugs so that even a small amount of deflection can cause one of the seals to leak A leaking pivot pin seal can lead to early replacement of the pivot pin assembly because it allows water and grit in between the pin and bushing and also because it permits lubricant to escape.
Many of the commercially available pivot pin designs also suffer from other drawbacks, such as, requiring tapped holes in at least one of the bucket brackets to attach the pivot pin to the bracket, requiring both the pivot pin and bushing to be replaced during joint servicing, requiring disassembly of the joint in order to relubricate the contact surfaces between the pin and bushing, are not symmetrical in design and, as such, do not allow for assembly from either side of the joint, requiring the pivot pin and bushing as a unit to be pressed or interference fit into the eye of the loader arm to assure rotation between the pin and bushing rather than the bushing and the loader arm eye, and/or relying on the body of the loader arm as a contact surface rather than the bushing.
In light of the foregoing, there is a need for an improved pivot pin assembly which addresses the abovementioned problems and drawbacks associated with current sealed and lubricated pivot pin arrangements.